Skin Cancer Linked with Lower Alzheimer's Risk

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Though it's smart to take steps to prevent skin cancer, people
diagnosed with the non-melanoma types of the disease may have a
reduced risk of developing Alzheimer's disease, a new study
finds.

Study participants who had been diagnosed with either
basal cell or squamous cell skin cancer were nearly 80
percent less likely to develop Alzheimer's, according to
researchers at Albert Einstein College of Medicine in New
York.

The researchers followed 1,102 people age 70 and older, for an
average of 3.7 years, checking them annually for Alzheimer's and
skin cancer. All participants were enrolled in an ongoing study
of aging in New York City.

At the beginning of the study, none of the participants had
signs of dementia or Alzheimer's, and 109 people reported
being diagnosed with either basal-cell or squamous-cell skin
cancer at some point previously.

During the study period, an additional 32 people developed one of
the skin cancers. While 126 people were diagnosed with some form
of dementia, only two people with
non-melanoma skin cancer developed Alzheimer's disease.

An estimated 2.8 million cases of basal-cell carcinoma, and
700,000 cases of squamous-cell skin cancer are diagnosed in the
United States each year, according to the Skin Cancer Foundation.
Basal-cell skin cancer develops in the deepest layer of the
epidermis, the skin's outer layer. Although it can be
disfiguring, the cancer usually doesn't spread if it's treated
early. On the other hand, squamous-cell skin cancer — which
affects the skin's topmost layers — can spread, and causes about
2,500 deaths each year.

What might link skin cancer with Alzheimer's risk still
isn't clear. "Biologically, the most interesting idea has to
do with cell division," Lipton said. "Alzheimer's is a disorder
in which brain cells die and aren't replaced."

Conversely, cancer occurs when "cells divide out of control to
form tumors," Lipton said, so one possible reason for the link is
that the process of nonstop cell division raises the risk for
basal- or squamous-cell skin cancer while lowering people's risk
of Alzheimer's, he explained.

But other factors may also play a role. Exercise has been shown
to lower the risk of Alzheimer's disease, Lipton said. "People
who run, canoe, bike or swim outdoors may get more sun exposure,"
increasing their risk for skin cancer at the same time they are
reducing their risk for Alzheimer's, Lipton said.

Another possibility is that exercising outdoors may boost levels
of Vitamin D, the so-called sunshine vitamin. "There is some
suggestion that Vitamin D has a
protective effect against Alzheimer's," Lipton said.

The findings show an association, not a cause-and-effect link,
between non-melanoma skin cancer and a reduced Alzheimer's risk.
However, Lipton said the association held even after the
researchers adjusted for diabetes, high blood pressure and
coronary heart disease, which may contribute to Alzheimer's and
other forms of dementia.

Despite what Lipton called "astonishingly strong" findings, he
stressed that more research is needed to confirm the results and
to tease out the mechanism that may be at work.

"It's hard to draw real specific conclusions from this study
because a small number of people — 141 — had skin cancer," said
Heather M. Snyder, director of medical and scientific operations
for the Alzheimer's Association.

"This study underscores the need to understand the underlying
biology of diseases like Alzheimer's and skin cancer, so we can
develop new targets and potential therapies," Snyder added.

Alzheimer's disease — the most common form of dementia — affects
memory, thinking and behavior. An estimated 5.1 million Americans
have Alzheimer's disease, according to the Alzheimer's
Association.

Because many people with a history of skin cancer develop
Alzheimer's, sun protection remains crucial. "People should still
wear sunblock and hats, and avoid sun exposure," Lipton stressed.
"Nobody would say, 'Go get a sunburn so you won’t develop
Alzheimer's.'"

The study appears today (May 15) in the journal Neurology.

Pass It On: Some skin cancers have been linked with a reduced
risk of Alzheimer's disease.